Desiccating apparatus



J. WHITING DESICCTING APPARATUS` Filed sept. 14. 1922 amarga ses. s, rasa hddd nnsrcca'rrne rAaa'rUs.

Application led. September 1s, 1922. lSerial No. 588,293.

To alli whom, t may concern.'

Be it known that I, JASPER WHITING, a citizen of the `United States, residin 4at Boston, in the county of Suolk and tate of Massachusetts, have invented certain new land useful Improvements in Desiccating Apparatus, of which the following is a specification.

This invention relates to apparatusfor desiccatingg purposes.

Apparatus of this character are generally based uponthe property of'certain materials to absorb moisture. The use of hygroscopic salt for the purpose of absorbing moisture has been resorted to for a long time.

The development, however, has taken place entirely along a single line, governed by the tendency to use as vmuch of the hygroscopic salt as possible.` 'f

It has been proposed in the past to use a porous body as a carrier of the hygroscopic material, but also in this case efforts have been made to crowd a maximum of 25 hygroscopicsalt into the pores ot the body,

the principal consideration beingthe application of as much of the salt as possible to make the absorptive capacity as large as possible.

ln contradistinctioi'i to the prior art-justreferred to l propose to construct dehydratingor desiccating units along entirely diterent lines governed by a specifically different principle. l propose to use a porous body as a carrier of the hygroscopic salt or absorbimg,r material in general, but instead or" merely using the body as a lcarrier of the hygroseopic material l propose to simultaneously take advantage of the capacity of the porous body 'to hold liquids.

in devices of thev prior art, the greater partand in fact nearly allY of the available pore space in the porous bodyhas been taken up by the hygroscopic material, leaving correspondingly little pore space for the water absorbed. The result has been that the. device could hold only a. limited amount ot water `and that as soon as this limit was reached, Water began to drip. While the absorptive capacity continued, 'there was no provision for holding the additionally absorbed water and the continued absorption was accompanied by release ot Water from tbe body, the rate ci releee being substantially equal to the yrate of fur-v ther absorption.

lIt is the principal object of this invention to provide a device of the character referred to rwhich will not drip under ordinary .atmospheric conditions.

It is a particular object to so proportion the amount of hygroscopic material and the `available .pore space of the porous body that a maximum absorptive capacity and holding capacity combined, according to the law of lmaxima and minima, is obtained.

The invention, generally and briefly stated comprises a suitable porous body and a hygroscopic material disseminated throughout the pores of tbe body in such quantity that Water considerably in excess, by Weight, of the hygroscopc material may be retained in the available pore space of the body.

For a full understanding'of the invention, its principle ofoperation and its advantages reference is had to the accompanying drawings in which Fig. 1 is aplan View.l of a dry-box for protecting food or other materials against the action of moisture, the cover being removed;

lig. 2 is a vertical section therethrough; an

Fig. 3 is a perspective vier7 of a slab or plate forming a lining for the walls ot' the box.

The box l0 may be of any suitable shape 'and size dependent upon the particular use for which it is intended.

Some or all the Walls or internal surfaces of the box are lined with slabs or plates il ,consisting of a suitable inert heat-resisting porous material such as asbestos products, porous clay bodies, filtros, inusorial earth or the like. These various materia' merely mentioned as representative of a large class ot materials available for the purposes of the invention.

As desiccating material there may be selee-ted any neutral or nearly neutral hygroscopic salt. For special reasons, however, to be more fully pointed out, l prefer laygrascop-ic salt which is non-volatile at re high temperatures, such as calcium Chlor for instance, etc.

Il avoid the use of acids or acid salts since they' are likely to attack any n etal with which they come into Contact, and l avoid una..

alkalies or alkalinesalts since they are likely' to take CO2 from the air and thus .lose their desiccating property.

A desiccating unit corresponding to slabs l1 in the drawings may be made in one of two ways:

l. A suitable porous mass, for instance asbestos board, may be impregnated with a solution of a suitable salt.

2. The unit may be formed synthetically from a mixture of a suitable salt, Water and porous material of the character referred to.

The distinguishing feature in either case isthe proportion of Water and the hygroscopic salt in question.

In the first of the ways proposed, the porous mass may be impregnated with a solution containing approximately of cal cium chloride, whereupon the water 1s driven o.

In the second method proposed, the prof' portion of the chloride and Water may be approximately 1:2 so thatlthe resulting unit when dried can take up twice as much water as there is calcium chloride present, assunring no shrinkage on drying and rewetting. This isobviously the equivalent of iinpregnating the porous body with a 33-% solution according to the first method.

After drying the slabs are preferably encased in non-corroding or non-corrodible metal coverings or screen cloth of gratings 12. These coverings serve to protect the slabs from abrasion and to prevent direct contact with the container and its contents. They also permit. the expeditious handling of the slabs, acting as a reinforcing trame.

The slabs may be held in place by iianges 13.

The lieat-resistii-'e material and the salts non-volatile at relatively high temperatures are chosen for combination so that the slabs may be subjected to heat to drive ofi' the' water and thereby regenerate the material for further use. YVhile within the range of materials available for this purpose various substances come under consideration, it'is advisable to select such materials and substances which withstand a temperature of say 300 C. without decomposition, disintegration or impairment of the normal function of the apparatus of which they form a part. Dehydration, however, should take place considerably below this critical temperature, preferably at about 100o C.

As previously pointed out, devices of this character have heretofore been based almost entirely upon the absorptive capacity of the hygroscopic material without regard to thc` holding capacity. I propose to combine the holding capacity or sponge action ot a por ous body with the absorptive capacity of a l hygroscopic material in such a way as to obnesaeze maximum relative humidity existing inv most localities over any considerable period of time. By equilibrim is meant that no moisture will be given up to or taken from the hygroscopic material if exposed to a gas containing (50% relative humidit l When hygroscopic salts other than calcium chloride are used the optimum proportion will vary somewhat from the above mentioned of one to two, but that ratio of Water to salt should be selected which will be in equilibrium with about 60% relative humidity and therefore not drip until after prolonged exposure to humidities exceeding this.

fhile I have specifically referred to the proportion of 1:2 for CaCl2, and to solutions in equilibrium with about 60% relative humidity for other salts, the invention is in -no Wise limited thereto- The proportion in yInode of or form for carrying out the objects ot the invention.

It is readily apparent that a device of the character described is particularly adapted for periodical regeneration and in fact the arrangement has had its inception in the idea of regeneration. However, the invention in its broader aspect is generally useful inasmuch as it provides a non-dripping unit ot high capacity as previously explained.

I claim:

1. A desiccating unit comprising a porous body and a hygroscopic salt disseminated throughout the porous body and partly filling the pore space, the arrangement being such thatI the amount of salt and the amount of Water adapted to be contained in the remaining pore space are in equilibrium in an atmosphere of about 60% relative humidity.

2.- A desiccating unit consisting of a porous mass of inert heat-resistive material `and a hygroscopic salt disseminated through JASPER wnirme. 

